Agents for inhibiting the corrosion of iron in acid solution

ABSTRACT

IN WHICH N MEANS AN INTEGER OF 1 TO 30 AND M STANDS FOR 0 OR 1 AND WHEREIN, IF N IS AT LEAST 3, IN THIS FORMULA II an amount of up to one third of the radicals which are enclosed by the bracket () can be replaced by radicals of the formula Corrosion inhibiting agents having the formula   IN WHICH R1 stands for an alkyl radical having 4 to 18 carbon atoms and bound in the 6-, 4- or 2-position to the benzene nucleus, R2 stands for hydrogen, an alkyl radical having up to 9 carbon atoms, or a radical of the formula   A stands for one of the anions Cl( ), Br( ), I( ), Ch3OSO3( ) and 1/2 SO4 ( )( ) in a quantity which is equivalent to the number of the positively charged sulfur atoms in the total molecule of the formula I, and X stands for a lower alkyl radical, the radical -C2H4OH or a radical of the formula

United States Patent 1 Heiss et al.

[4 1 Nov. 20, 1973 [54] AGENTS FOR INHIBITING THE CORROSION OF IRON IN ACID SOLUTION [75] lnventors: Lorenz l-leiss, Hofheim, Taunus;

Martin Hille, Bad Soden, Taunus, both of Germany {73] Assignee: Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius & Bruning, Frankfurt, Germany 221 Filed: Dec. 21, 1971 211 Appl. No.: 210,558

[30] Foreign Application Priority Data Dec. 28, 1970 Germany P 20 63 987.6

[52] US. Cl 252/147, 252/148, 252/149, 252/151, 252/395 [51] Int. Cl Clll 7/34, C23g 1/06 [58] Field of Search 252/149, 151, 147, 252/395, 87, 181; 260/607 B [56] References Cited UNITED STATES PATENTS 4/1937 Lieber et al. 252/77 X 6/1938 Piggott 2,941,949 6/1960 Saukaitis 252/ 151 3,060,156 10/1962 Rassweiler 260/79 3,216,979 11/1965 Sexsmith et a1. 260/79.3 3,668,137 6/1972 Gardner 252/151 X Primary Examiner-Leon D. Rosdol Assistant Examiner-Harris A. Pitlick Att0rneyArthur G. Connolly et a1.

[57] ABSTRACT Corrosion inhibiting agents having the formula 1 6 2| 5 FBI R 4 2 V 7. v t

in which R, stands for an alkyl radical having 4 to 18 carbon atoms and bound in the 6-, 4- or 2-position to the benzene nucleus, R stands for hydrogen, an alkyl radical having up to 9 carbon atoms, or a radical of the formula X (IV) in which n means an integer of 1 to 30 and m stands for 0 or 1 and wherein, if n is at least 3, in this formula 11 an amount of up to one third the radicals which are enclosed by the bracket can be replaced by radicals of the formula 0 0,11,- s c 11,, (-CCH2),,,

8 Claims, No Drawings AGENTS FOR INHIBITING THE CORROSION OF IRON IN ACID SOLUTION ln the industry, the inhibition of the corrosion of iron and iron alloys constitutes a serious problem. The inhibition of the corrosion is particularly difficult when acids are used simultaneously.

Attempts have already been made to obtain an inhibition or reduction of the corrosion of iron or iron alloys by application of organic or inorganic compounds. As such corrosion inhibitors, the most various compounds such as higher molecular amines, quaternary ammonium compounds, organic phosphonium compounds, sulfonic acids, fatty acids, thio-ureas, mercaptans, alkyl sulfides and alkyl sulfoxides as well as heterocyclic compounds with oxygen, sulfur or nitrogen as hetero-atoms have been proposed.

Corrosion inhibitors are used mainly in the surface cleaning of iron and iron alloys, where, in general, aqueous acids are employed for the removal of rust, scales and the like. The action of the acid is to be controlled in such a manner that the surface impurities are attacked and the material itself remains unaffected. To reach this goal, special inhibitors are used.

The present invention provides new corrosion inhibitors which permit a better protection of iron and iron alloys in acid solution. The invention furthermore relates to the use of these new inhibitors in the known industrial processes, for example in the surface cleaning of metals, wherein iron or iron alloys are subjected to the action of acid solutions.

Accordingly, the present invention provides agents which inhibit the corrosion of iron or iron alloys in acid solution and which essentially consist of, or contain as the active component, compounds of the formula I m H HO-C2H4-S-X in which X represents an alkyl group having I to 4 carbon atoms, the group C H -OH or a group of the formula ll in which n represents numbers from 1 to 30 and m represents or I and wherein, if n is at least 3, in this formula ll an amount of up to one-third of the radicals which are enclosed by the bracket can be replaced by radicals of the formula R represents a straight chain or branched alkyl group having 4 to 18 carbon atoms bound in the 6-, 4- or 2- position to the benzene nucleus, R represents hydrogen, a straight chain or branched alkyl group having 1 to 9 carbon atoms or a group of the formula in which X has the meaning given above, A represents the anions Cl Br I", CH OSO 1/280 in a quantity which is equivalent to the number of the positively charged sulfur atoms in the total molecule of the formula I.

In addition, it is advantageous to add to the corrosion inhibitors of the invention small amounts of up to about 15 percent by weight, referred to the sulfonium salts of the formula I, of alkynols, preferably propargyl alcohol. The new corrosion inhibitors may be applied together with other known corrosion inhibitors, other auxiliary agents, for example surface-active agents. 7

The sulfonium salts of the formula I used according to the invention as corrosion inhibitors can be prepared by transforming a monoalkylor dialkyl-benzene be chloromethylation into the corresponding alkylor dialkyl-benzyl chloride and reacting the latter with an alkali mercaptide of thioethylene glycol to obtain the corresponding thio-ether:

+ olomocm @-cmo1 0111011 may be prepared, for example according to the method described in Houben-Weyl, Methoden der organisehen Chemie," volume 14/2 (1963), page 586. The polythio-diethylene-glycol ethers or the polythiodiethylene glycol formals-can then be reacted in known manner with alkyl-benzyl halides to yield the corresponding alkyl-benzyl-sulfonium salts. The reaction can be carried out by mixing the substances with stirring, if necessary in the presence of solvents, at room temperature or, if necessary, while heating. An addition of metal halides, such as zinc chloride, has an ac celerating effect in the reaction.

As alkyl benzenes 'which may be used as starting materials for the preparation of the sulfonium salts of the formula I, there may be mentioned, for example hexylbenzene, octylbenzene, tetra. propylene-benzene, dodecylbenzene, 4-tert.-butyltoluene, n-nonylbenzene or an industrial alkyl-benzene mixture having alkyl groups of 12 to 18 carbon atoms.

The chloromethylation of these alkyl-benzenes can 126 g 1 mole) of dimethyl sulfate were added dropwise, at 40 C, while stirring, to the tetrapropylenebenzyl-B-oxethyl sulfide and the whole was stirred for 2 be effected in a manner known per se, for example by ho r The p-tetrapropylenebenzyl-S-oxethyl-S- reaction with methylchloromethyl ether and Friedel- 5 m8thyl-S-Sulf0nium-methosulfate was obtained in the Crafts catalysts, for example zinc chloride or concenform fa C u il ith a yield of46l g and was found trated sulfuric acid. Depending on the quantity used of t b6 Clearly Soluble n rmethylchloro-methyl ether, there can be introduced Prepamlio" of P y y g y one or two chloromethyl groups into the benzene ring, dodeeylbel'llyl-sUlfonillm Chloride so that compounds such, for example, as p-dodecylben- 122 g (1 mole) of thiodiethyleneglycol and 30 g (1 zyl-chloride, 2-chloro-methyl-4-tert.butyltoluene, 2,4- mole) of paraformaldehyde in 500 ml of benzene were bis-chloromethyl-dodecylbenzene etc. are obtained. combined with 20 g of a H -ion exchanger resin and The sulfonium salts of the formula I are excellent corheated under reflux, while removing in about about rosion inhibitors for iron and iron alloys in acid soluhours about 17 ml of water by azeotropic distillation. tions. They can be used in all those cases where aque- Th i exchanger was filtered off and the solvent ous or aqueous acid solutions are allowed to act on iron was removed. The poly-thiodiethyleneglycol-formal or iron alloys, for example in metal pickling baths for obtained in the form ofa viscous oil with a yield of 131 surface cleaning of iron or in similar processes. g was found to have a molecular weight (measured os- The sulfonium salts of the formula 1 used according mometrically in benzene) of 546 and a content of to the invention are added to the acid metal treating 20 bound formaldehyde of 22.7 percent. baths in such a quantity that their concentration in the The p0]y thiodiethyleneglycopformal was combined baths is at least Pereem by Weight; Preferably, the with 300 g 1 mole) ofp-n-dodecylbenzyl chloride, 500 concentration is adjusted to a range of from 0.1 to 1.0 ml f isopropanoi and 50 g f i chloride, and the P y Weight- Though an upper limit for the mixture was heated for 8 hours under reflux. Then, 500 centration of the corrosion inhibitors of the invention m] f benzene were added, while stirring, and the whole does not exist. a Concentration of Percent y Weight was washed several times with saturated aqueous NaClwill in general not be exceeded for economical reasons, solution to remove the zinc chloride. The solvent was the more so since a higher concentration in most cases removed b di ill i i a rotary evaporator Th 1. does not improve the protection against corrosion. ln 3O .thi di th l gl ol f al-d d ylbe l special ea e the in i Concentrations may be sulfonium chloride was obtained in the form ofa highly higher or lower than the indicated limits, if necessary. viscous oil with a yield of 421 g. The product contained The preparation of the sulfonium salts of the formula 10 5 r ent by weight of ionogenically bound chlol of the present invention is illustrated in the following rine. Examples: The following Examples show the advantageous anti- 1. Preparation of p-tetrapropylenebenzyl-S.oxethyl-S- corrosive action of the sulfonium salts of the invention. methylsulfonium-methosulfate For testing the inhibiting effect, cleaned and weighed 300 g (1 mole) of tetrapropylene-benzyl chloride, iron plates (soft steel RST 37-2-05), having a size of 75 obtained in known manner from tetrapropylene- X 10 X 0.75 mm each, were treated at 80 C in an aquebenzene and methyl-chloromethyl ether and zinc chlo- 40 ous solution containing 80 percent by weight of hydroride or concentrated sulfuric acid were combined, chloric acid and (a) 0.05 percent by weight, b) 0.1 perwhile stirring, with 78 g (1 mole) of B-hydroxyethylcent by weight or (c) 0.15 percent by weight of one of mercaptan and then with 40 g 1 mole) of sodium hythe following inhibitors. Subsequently, the loss in weigdmxide d h h l was h i d f 5 hours at ht of the plates and thus the steel removal were estab- 50 0 C 200 m] f water and 200 of benzene lished and indicated as a measure for the anticorrosive were added, while continuing stirring, and the benzene effected attainedphase was separated. The benzene solution was washed In the tests, the inhibitors of the invention were comseveral times with water, dried and the solvent was repared with anticorrosives which do not fall within the moved by distillation. Tetrapropylenebenzyl-B-oxethyl scope of the present invention and which are indicated sulfide in the form of a light yellow oil was obtained in in the Table hereinafter sub No. 13 to 16. The results a yield of 335 g 98 percent) having a content of orof these comparative tests demonstrate the superior anganically bound sulfur of 9.3 percent (theory 9.36 perticorrosive effect of the sulfonium salts according to cent) and a molecular weight of 338 (theory 342). the invention.

Concentration, steel removal (loss) in g./m.

Product 9. b c

H (-cilcuz)i@cm s CH O s 0 w CHa 2 CH3 c mon 98 60 52 lI(-(iH-CH2)- -CHQ 2(71130 s 04 CZILiOH CH m/ CH2-S 3 Equimolar mixture of 1 and 2 A 100 66 54 Concentration, steel removal (loss) in tip/m.

Product 11 b 1- Q11 -c11--s {1 1 c1 m/ C12H25 CH2lC2H5 CU) cums-@cm-N O c1 We claim: '5 CH3 /C=H1OH 1. An acid metal treating bath consisting essentially O 2CH30S03" of hydrochloric acid and as a corrosion inhibitor 0.05 to 2.0 percent by weight of a compound of the general C2H40H formula F M w H0-C2H4-SX 20 CH:

3. An acid metal treating bath consisting essentially 6 1 2| of hydrochloric acid and as corrosion inhibitor 0.05 to c? R1 2.0 percent by weight of an equimolar mixture of the 4 compounds of the formulae in which X represents an alkyl group having 1 to 4 carin which n represents numbers from 1 to and m represents 0 or 1 wherein, if n is at least 3, in this formula [I an amount of up to 1/3 of the radicals which are enclosed by the bracket can be replaced by radicals of the fonnula R, represnets a straight chain or branched alkyl group having 4 to 18 carbon atoms bound in the 6-, 4- or Z-position to the benzene nucleus,

R represents hydrogen, a straight chain or branched alkyl group having 1 to 9 carbon atoms or a group of the formula in which Y represents an alkyl group having 1 to 4 carbon atoms or the group --C- ,H OH, A represents the anions Cl, Br", 1", CH OSO l/2SO in a quantity which is equivalent to the number of the positively charged sulfur atoms in the total molecule of the formula I.

2. An acid metal treating bath consisting essentially of hydrochloric acid and as corrosion inhibitor 005 to 2.0 percent by weight of a compound of the formula CH3 C2H4O H 6 (+1/ (-1 H( HCH2)4 CH1s CH OSO 3 O and CH3 C2H4O H m-oH-cm). O CH1S\ 201-1 050;

CH; C 1H4 O H 4. An acid metal treating bath consisting essentially of hydrochloric acid and as corrosion inhibitor 0.05 to 2.0 percent by weight of a compound of the formula 5. An acid metal treating bath as claimed in claim 1, which additionally contains up to 15 percent by weight, referred to the sulfonium salt corrosion inhibitor, of an alkynol.

6. The acid metal treating bath as claimed in claim 1 wherein R represents a group of the formula 9 10 wherein Y is an alkyl group of l to 4 carbon atoms. 01H

7. The acid metal treating bath as claimed in claim 6 8. An acid metal treating bath consisting essentially H1 of hydro-chloric acid and as a corrosion inhibitor 0.05 5 to 2.0 percent by weight of a compound of the general CH3 formula H H(( JHC1)4 Hz 

2. An acid metal treating bath consisting essentially of hydrochloric acid and as corrosion inhibitor 0.05 to 2.0 percent by weight of a compound of the formula
 3. An acid metal treating bath consisting essentially of hydrochloric acid and as corrosion inhibitor 0.05 to 2.0 percent by weight of an equimolar mixture of the compounds of the formulae
 4. An acid metal treating bath consisting essentially of hydrochloric acid and as corrosion inhibitor 0.05 to 2.0 percent by weight of a compound of the formula
 5. An acid metal treating bath as claimed in claim 1, which additionally contains up to 15 percent by weight, referred to the sulfonium salt corrosion inhibitor, of an alkynol.
 6. The acid metal treating bath as claimed in claim 1 wherein R2 represents a group of the formula
 7. The acid metal treating bath as claimed in claim 6 wherein Y is -CH3.
 8. An acid metal treating bath consisting essentially of hydro-chloric acid and as a corrosion inhibitor 0.05 to 2.0 percent by weight of a compound of the general formula 